I have the same problem with my Toshiba Tecra M7 on which I just installed lucid with kernel 2.6.32-24-generic.
I have installed the package linux-backports-modules-wireless-lucid-generic, but I still get disconnects, even while browsing.

Here's lshw -C network:
*-network
       description: Wireless interface
       product: PRO/Wireless 3945ABG [Golan] Network Connection
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: wlan0
       version: 02
       serial: 00:18:de:4e:e5:2f
       width: 32 bits
       clock: 33MHz
       capabilities: bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwl3945 driverversion=2.6.32-24-generic firmware=15.32.2.9 ip=192.168.100.8 latency=0 multicast=yes wireless=IEEE 802.11abg
       resources: irq:28 memory:ffcff000-ffcfffff

Here from kern.log:
Sep 22 00:11:59 dknux kernel: [18696.790462] iwl3945 0000:03:00.0: Microcode SW error detected. Restarting 0x82000008.
Sep 22 00:11:59 dknux kernel: [18696.790500] iwl3945 0000:03:00.0: Start IWL Error Log Dump:
Sep 22 00:11:59 dknux kernel: [18696.790506] iwl3945 0000:03:00.0: Status: 0x000202E4, count: 1
Sep 22 00:11:59 dknux kernel: [18696.790511] iwl3945 0000:03:00.0: Desc       Time       asrtPC  blink2 ilink1  nmiPC   Line
Sep 22 00:11:59 dknux kernel: [18696.790738] iwl3945 0000:03:00.0: SYSASSERT     (#5) 1615053811 0x008B6 0x00274 0x00320 0x01472 116
Sep 22 00:11:59 dknux kernel: [18696.790741]
Sep 22 00:11:59 dknux kernel: [18696.790871] iwl3945 0000:03:00.0: Start IWL Event Log Dump: display last 20 count
Sep 22 00:11:59 dknux kernel: [18696.790914] iwl3945 0000:03:00.0: 1614987569   0x00000080      0313
Sep 22 00:11:59 dknux kernel: [18696.790938] iwl3945 0000:03:00.0: 1614987571   0x000001fe      0501
Sep 22 00:11:59 dknux kernel: [18696.790963] iwl3945 0000:03:00.0: 1614988327   0x00000000      0502
Sep 22 00:11:59 dknux kernel: [18696.790988] iwl3945 0000:03:00.0: 1614989119   0x000000c3      0310
Sep 22 00:11:59 dknux kernel: [18696.791012] iwl3945 0000:03:00.0: 1614989120   0x00000000      0314
Sep 22 00:11:59 dknux kernel: [18696.791037] iwl3945 0000:03:00.0: 1614989121   0x0000031a      0501
Sep 22 00:11:59 dknux kernel: [18696.791061] iwl3945 0000:03:00.0: 1614989126   0x000003fc      0504
Sep 22 00:11:59 dknux kernel: [18696.791086] iwl3945 0000:03:00.0: 1614989127   0x6042c744      0503
Sep 22 00:11:59 dknux kernel: [18696.791111] iwl3945 0000:03:00.0: 1614989127   0x00000010      0503
Sep 22 00:11:59 dknux kernel: [18696.791136] iwl3945 0000:03:00.0: 1614989128   0x0b0188bc      0503
Sep 22 00:11:59 dknux kernel: [18696.791161] iwl3945 0000:03:00.0: 1614989129   0x6042c744      0503
Sep 22 00:11:59 dknux kernel: [18696.791185] iwl3945 0000:03:00.0: 1614989129   0x00000010      0503
Sep 22 00:11:59 dknux kernel: [18696.791210] iwl3945 0000:03:00.0: 1614989130   0x0b0188bc      0503
Sep 22 00:11:59 dknux kernel: [18696.791235] iwl3945 0000:03:00.0: 1614989132   0x0b0188b4      0500
Sep 22 00:11:59 dknux kernel: [18696.791259] iwl3945 0000:03:00.0: 1614989134   0x0b0188b4      0600
Sep 22 00:11:59 dknux kernel: [18696.791284] iwl3945 0000:03:00.0: 1614989134   0x00000000      0600
Sep 22 00:11:59 dknux kernel: [18696.791308] iwl3945 0000:03:00.0: 1615024979   0x00000000      0301
Sep 22 00:11:59 dknux kernel: [18696.791333] iwl3945 0000:03:00.0: 1615025361   0x00000000      0304
Sep 22 00:11:59 dknux kernel: [18696.791357] iwl3945 0000:03:00.0: 1615053809   0x00000002      0123
Sep 22 00:11:59 dknux kernel: [18696.791382] iwl3945 0000:03:00.0: 1615053812   0x00000100      0125
Sep 22 00:11:59 dknux kernel: [18696.791402] iwl3945 0000:03:00.0: Error Reply type 0x00000005 cmd REPLY_TX (0x1C) seq 0x0250 ser 0x00740000
Sep 22 00:11:59 dknux kernel: [18696.803325] iwl3945 0000:03:00.0: Can't stop Rx DMA.